Electric arc furnaces are constructed with a domed roof consisting essentially of silica or refractory block embraced at the base with a metallic furnace roof ring. The roof is generally dome shaped and has a plurality of openings through which the furnace electrodes extend. The pattern or arrangement of the electrodes may vary among the various furnace manufactureres or different size furnaces so that different roof opening patterns are required.
The furnace roofs gradually deteriorate during use and must be replaced. The replacement roof structure is constructed on-site on a form and the roof is lifted into place on the furnace top. Heretofore it has been commom practice to provide a different roof form for each different size roof or electrode pattern arrangement. A separate form for each different roof size and pattern arrangement is space consuming and expensive.